Method of sizing and grooving composite strip material



De# 17, 1940 J; mHlLnAaoL-r 2,225,269

METHOD 0F SIZING AND v(IROVING COMPOSITE STRIP MATVER-IALI4 Filed June 24, 19:58

Y ffy-1 ATTORNEY Patented Dec. 17, 1940 PATENT oFrl-CE METHOD F SIZING AND GROOVING COMPOSITE STRIP MATERIAL John M. Hildabolt, Dayton, Ohio, assignor to General Motors Corporation, Detroit, Mich., a corporation of Delaware Application :une 24, 193s, semi No. 215,640 501mm. (0L zei- 1495)V This invention relates tc a method of preparing composite flat stock for use in the fabrication of bushings, and is particularly concerned with the formation of oil grooves or depressions therein.

6 The object of the invention is to provide a method for sizing composite metal flat stock and simultaneously forming a depression in the surface thereof whereby the surface of the stock is substantially flat and the depression is devoid of l0 overhanging edges. y

In carrying out the above object a further object is to carry out the method on composite stock comprising a porous metal layer preferably attached to a strong metal supporting back.

1| Further objects and advantages of the present invention will be apparent from the following description, reference being had to the accompanylng drawing wherein a preferred embodiment of the present invention is clearly shown.

20 The usual method of forming oil. grooves in bearing stock has been to stamp the groove in a strip of metal before the fabrication of a bushing therefrom. This stamping operation displaces the metal at the edges of the grooves so as to 25 form a projection or bump along the edges of the groove. This displaced metal varies in quantity according to the metal used in the bearing blank.

metal is displaced along the edges of the groove a0 and therefore the removal of the same does not present any serious production problem during formation of the bushing. On the other hand, if bi-metallic strip material is used', which includes a soft metal layer, the displaced metal presents a a real problem. Thus when grooving composite strip material which includes a soft metal layer thereon, such as a porous metal bronze layer, the displaced metal at the edges of the groove is in excessive quantities, and when the porous metal 40 is sized by subsequent application of pressure and formed into a bushing, the displaced metal forms an overhanging lip at either edge of the groove and in some cases substantially closes the groove. The present invention solves this dim- Lculty while simultaneously providing a method which is more economical from a production angle.

In the drawing: 1 I Fig. l represents a fragmentary view, on an 5o enlarged scale, of a piece of strip material with the sintered metal layer tmsized.

Fig. 2 is a fragmentary view, on an enlarged scale, showing the grooving and sizing punch just prior to its engagement with the composite 5s Strip.

' matrices which are well known to those Fig. 3 is a fragmentary -view, on an enlarged scale, showing the grooving and sizing punch in position at an intermediate stage of the grooving operation, wherein the groove is partially formed and the porous metal layer is as yet unsized'. 5 Fig. 4 is a fragmentary view, on an enlarged scale, showing the grooving and sizing'punch in its final position relative to the composite strip and after the porous metal layer has been sized and grooved. i

Fig. 5 is va plan vview of a bearing blank after the grooving operation, and l vFig. 6 is an end view of a cylindrical bushing, on an enlarged scale, as formed from the blank shown in Fig. 5. l5 Referring to the drawing, and particularly Fig. 1, a soft metal layer 2li is shown bonded to a strong metal supporting back 22. The layer 2li may be of babbitt or it may be porous metal such as; bronze, bronze rhaving graphite dispersed A therethrough, copper-nickel alloys, ferrous alloys, or any of the conventional porousmetal skilled in the art. The supporting back l2 is preferably steel or it may be fabricated from some nonferrous metal according to the specic use to which the bushing is to be applied. When rolled bronze strip is utilized, very'little Composite stock including a porous metal layer may be made by a number of different processes, for example, the porous metal may' be formed' by 30' briquetting metal powders into a sheet or layer which is .sintered together under non-oxidizing conditions, said sheet subsequently beingplaced on a supporting back and heated while under Apressure to cause bonding thereto. One of the more recent developments in this art is to provide a layer of powdered metal on the supporting back either with or without compression, and then sinter the assembly, 'at a suitable temperature, so as to alloy the metal powders in' situ on the 40 back, and simultaneously bond Ithe porous metal layer thus formed to the supporting back. Obviously, when this method is carried out without the initial compression of the powdered metal layer, the resultant porous metal layer is of greater porosity and is therefore more compressible than when initial compression is utilized. Composite strips made by this latter process present even greater problems in production when an oil `groove is. to be formed therein, due to the compressibility of the layer. The method disclosed herein is su'fllciently flexible to be utilized with any of this composite stock. The drawing is directed to the use ofthe method in connection with composite stock including a por'ous metal layer.

Fig. 2 shows a die 2l, which includes a projecting portion or rib 28 thereon, and a flat portion 28. The rib 26, in the preferred form. is dimensioned so that its projection does not exceed, and preferably is slightly less than, the vdepth of the unsized porous metal layer. Thus as the die is pressed downwardly against the porous metal layer the rib 26 embeds itself into the porous metal layer 20 to form a groove 30 therein. Further downward movement of the die 24 causes the flat surface 28 to'engage the fiat surface of the unsized porous metal layer 20, thus the entire surface of the metal layer is compressed, to size the porous metal layer. This operation resulates the thickness of the porous metal layer and also controls the hardness of the layer. It is apparent that as the porosity of the layer is reduced the hardness thereof is increased. During this sizing operation the rib 28 continues to impress the oil groove in the porous metal layer, and in the embodiment shown in the drawing, referring specifically to Fig. 4, presses the oil groove and a layer of the porous metal into the strong metal back 22. While the hereinbefore disclosed grooving operation is preferred, it is apparent that the sizing and grooving may be controlled so that the rib portion 26 of die 2Q does not press directly into the metal backing, but only grooves the porous metal. Figs. l through 4, are sections such as would be taken on line A-A. shown in Fig. 5.

For illustrative purposes only the following specific 'example' is given, a steel strip .050" thick is provided with a porous metal layer .028" thick when unsized. The grooving die projection or rib has a height of .021". It is apparent therefore that the grooving rib is .007" less in height than the thickness of the unsized porous metal layer. Upon compression, the sizing die reduces the thickness of the porous metal layer to .013" which causes the grooving rib to groove the steel back to a depth of .008 in the preferred form. is hereinbefore set forth, the grooving rib may be so dimensioned that the steel remains ungrooved, such modification being fully within the scope of the present invention.

It is apparent, by utilizing the present procedure, that the metal adjacent the edges of the oil groove 30 is displaced as at 32, but due to the fiat surface 2B of the die engaging the fiat surface lof the metal and compressing the same, that this displaced metal is pressed back into place while at the same time the rib 26 maintains the shape and size of the oil groove. This simultaneous operation is further desirable, since there is a possibility of the soft metal being sheared from the supporting back if the groove is formed to the'preferred depth without simultaneous sizing, or compression. The present invention therefore provides a method for simultaneously sizing the soft metal layer of a composite strip, and impressingA an oil groove therein. The method is economical since both operations are carried out by a single stroke of the die, and the product is uniform and free from distortion. The problems heretofore present have been eliminated, and an undistorted, flat surfaced grooved blank of composite metal is produced which may subsequently be rolled into cylindrical bearings yas shown in Fig. 6, or which may be formed into semi-cylindrical bearings in view of the contemplated use thereof. In the herein disclosed process the soft metal, or porous metal layer is continuous, extending into the base of the groove Without breaks, as noted in the drawing.

Various modifications of die design to accomplish substantially the same results are Within the scope of my invention. One of such modifications consists ofutilizing a compound die in which the fiat surface of the die comes into contact with, and clamps the soft metal surface prior to the entry of the grooving punch. After partial entry of vthe grooving punch, the flat surface of the die may further compress the soft metal surface if desired. Still another modification for use with composite stock, including a babbitt layer thereon, consists in merely sizing the stock adjacent the edges of the oil groove, thus preventing the displacement of metal at this point. Manifestly the fiat surface of the babbitt is not sized, since it is substantially non-oompressible and does not require such a sizing operation.

While the embodiment of the present invention as herein disclosed, constitutes a preferred form, it is to be understood that other forms might be adopted, all coming within the scope of the claims which follow.

What is claimed is as follows:

1. A method of preparing flat composite stock comprising a soft layer of a sintered metal formed from metal powder bonded to a strong metal supporting back for subsequent use in the fabrication of bushings, comprising the steps of compressing a limited area only of said soft metal layer to form a depression therein and then while continuing the pressure on said limited area compressing the area adjacent of said depression for simultaneously sizing the metal at the edges of the depression, and finally forming the depression to the desired depth.

V2. A method of preparing flat composite stock comprising a sintered porous metal layer bonded to a strong metal supporting back for subsequent use in the fabrication of bushings, comlprising the steps of partially forming an oil groove in the porous metal layer by applying pressure on the limited area of said porous metal layer, then initially compressing the remainder of said porous metal layer, continuing the formation of said oil groove, and then finally compressing the entire surface of the porous metal layer reducing the thickness of the layer to the thickness -desired, and simultaneously lfnorming the oil groove into the strong metal ack.

3. The method of preparing flat sintered porous metal stock for subsequent use in the fabrication of bushings comprising, forming a highly porous layer by sintering together powdered metal, and then compressing the stock in a die for forming a depression therein, and for simultaneously reducing the thickness of the stock to the thickness desired, thereby regulating the hardness and porosity of the porous metal layer.

4. A method for preparing flat composite stock for the subsequent use in the fabrication of bearing elements comprising the steps of, forming composite stock by bonding a layer of porous metal formed from metal powder to a strong non-porous metal supporting back, and then compressing the entire surface of the porous metal layer for forming an oil groove therein and for simultaneously sizing the fiat surface of the porous layer by reducing the thickness of the entire layer.

5. The method for preparing flat composite mainder of the surface of said porous metal layer while continuing pressure on said limited area. for forming an oil groove in the surface of said porous metal layer and for simultaneously sizing the nat surface of the porous metal layer 5 by reducing the thickness of the entire layer.

JOI-1N M. HILDABOLT. 

